In a world with humanized (or at least tool using) reptiles, how long would a tattoo be able to last on the scales? Would the tools need to be much different than what we use today?
Would it be possible for a reptile to get a tattoo of a human?
In a world with humanized (or at least tool using) reptiles, how long would a tattoo be able to last on the scales? Would the tools need to be much different than what we use today?
Would it be possible for a reptile to get a tattoo of a human?
The main problem with this concept is that scales are constantly shed over the lifetime of the reptile. As a result any sort of skin decoration would be by its nature temporary. I think it's more likely that they would develop things similar to our nail polish and use that to paint their scales in various designs and styles to accomplish a similar purpose to tattoos but in not so permanent a way.
Tattoos are ink that's injected below the skin, and visible through the skin. You would need translucent scales for that to work. And scales are shed throughout a reptile's lifetime - so tattoos (on the scale itself) would be temporary.
There's a book about an alien who used a human as his totem. Demon of Undoing And humans use reptiles as decoration, so why not the reverse?
Based on the comments made before me, tattooing on the scales isn't gonna work because they shed these. This made me come of with a more intrusive, but possible, solution:
DNA-tattooing (or the closest thing to it). The scales get a color from the DNA of the owner, why not a changes locations of DNA, making it like pixel-art, depending on the size of the scales.
Does requires a little futuristic mindset.
You could likely have some method of scarification work. If you forcibly remove healthy scales from the reptile and damage the cells which control their replacement. The resultant scar tissue may be perminant damage that looks different from the scales. I do not know if this would actually work on a real reptile but I would definitely believe it for a fictional reptilian humanoid. Depending on the nature of the scars, you may be able to stain/tattoo the scar tissue. I think it would be relatively easy to imagine an cool, intricate pattern of missing and present scales.
Thanks to the points mentioned in other answers, I could direct a more extensive research, and this is the most satisfying result I got. Disclaimer: I went into much details because it seemed like there was a few misconceptions on how reptilian scales work.
TL;DR: Unless the scales are transparent, the tattoo has to be done on the scales and as such, it is not going to be permanent at all because of the frequent shedding.
First of all, let's clarify some points. Scales are extension of the epidermis, just above the dermis; depending on the kind of reptile, they can be very thin folds of the epidermis (e.g. snake scales), or thickened areas of epidermis (crocodile scales). You can find some good illustrations of these in the part 1 of this ZooPax. Normally (i.e. on humans), tattoos are injected in the dermal layer. This would mean sub-scale tattooing, which can be a problem for snake-like scales. However, if the scales are thick enough, we could get away with simply injecting the ink in the epidermis itself (so the scales) rather than in the dermis. However, things are not quite that simple.
As Tim-B and user3082 mentioned, the biggest issue is that reptiles shed their skin (or moulting, if we go for the technical term) frequently. Each type of reptile moult differently; snakes do it by turning their skin inside out like a sock, most lizards moult in patches, though some do it all in one go. Crocodiles and turtles have a very different kind of scales; they shed them one at a time, but if we can simply tattoo them in the dermis directly, then it is not an issue. So, in either case, the solution would be to tattoo reptiles the same way we tattoo humans, by injecting the ink in the dermis; regardless of how we would do it for snake or lizard scales. Cort Amon mentioned a solution for that involving syringes and dye (though it can also be done with laser technology, it seems).
However, even then, there is still another problem: it's a moot point to tattoo in the dermis if we can't see through the scales!
Solutions can differ greatly whether the scales are transparent or not (or if they even can be), so I'll treat both of those possibilities.
In that case, tattoos wouldn't be permanent because you would need them to be in the scales themselves rather than under them; you can think of them as an equivalent to our hair dyes. They would last several months (maybe even a year or more depending on the kind of reptile), but would eventually disappear as the skin is shed.
However, Tim B suggested an interesting alternative in his answer, although even more temporary:
I think it's more likely that they would develop things similar to our nail polish and use that to paint their scales in various designs and styles to accomplish a similar purpose to tattoos but in not so permanent a way.
This is actually something that is done nowadays already for marking reptiles in the wildlife (Johnson, M. A. "A new method of temporarily marking lizards." Herpetological Review 36. 2005: 277–279). I could imagine this solution to be less restrictive than tattooing, notably with colours, as bright hues would be more easily achievable. Also, glitters. I don't think I need to say more.
As Gertlx pointed out, reptile scales are made of keratin, meaning it is possible for scales to be transparent. However, this is still not enough. If the scales are too thick, the tattoo might be hard or even impossible to see through the scales.
To sum it up, then, for a reptile to be tattooed in the strictest sense of the term (i.e. with ink injected in the dermis), and for the tattoo to actually be permanent, you need the reptile to:
Speaking of which, let's answer the second part of the question.
Would the tools need to be much different than what we use today?
For crocodile-like scales, the method would be the same as for humans, although the tattoo machine would need to be stronger to be able to poke through the reptile leather. If the tattoo is made manually (e.g. Tebori), this is less of an issue, as the force put in the tool is more easily controlled.
For snake-like scales, it becomes much more complicated. Using the traditional method would probably get unsatisfactory results for reaching the dermis without damaging the scales too much. By using syringes or similar tools, one could inject the ink by going under the scales, but I believe this wouldn't allow a tattoo to be as elaborate as with the other method.
If the intent is simply to tattoo on the scales however, then the tattoo gun would do the job just fine.
And finally:
Would it be possible for a reptile to get a tattoo of a human?
Possible? Definitely. Adeptus mentioned The dragon with the girl tattoo, in which the protagonist, a female dragon, has a tattoo of a human girl; it is considered to be a mythical creature in that world. user3082 talked about another possibility as seen in Demon of undoing, where an alien takes the human race as some kind of role model.
Whether humans exist or not in the universe we're working with, there can always be a plausible explanation as to why one would have a tattoo of a human.
Extra reading content:
Tattooing reptiles has actually been done before and is still in actuality. There is an article about the methods of marking small animals (Ngaio J. Beausoleil, David J. Mellor, Kevin J. Stafford. "Methods for marking New Zealand wildlife." 2004.); tattooing reptiles is described on page 82.
The way I would approach this is to modify the cells that produce scales - and have any design as a series of scale shaped pixels.
This would mean that the effect would be permanent, as each new scale grown to replace a shed one would retain the colour, unlike simply painting the sales.
If they are suitably advanced they could get tiny bio-luminescent particles embedded in each scale, and use their external surfaces to display patterns and pictures at will.
Provided the species has natural scale patterns, it would be possible as follows.
The cells that generate the scales would have the ability to generate some pigmentation for the scales naturally.
This would not a binary switch set at birth. Rather the amounts of pigments generated would vary based on the chemical environment around the cell activating genes with different frequencies. The process would presumably be self-stabilizing, ie. generating lots of or little of pigment this round would have the corresponding effect on the next round. This, or equivalent mechanism, is plausible, if the natural patterns are stable.
It would be possible to change of the chemical state of the progenitor cells simply by injecting chemicals into the tissue. Self-evident, but depends on the chemical. Tools used for tattooing should be sufficient, especially if done at a time when the reptile is changing skins. Alternately, if this an initiation ritual and the reptiles have decent ability to regenerate their scales, scales could be removed in strips and the design then be painted directly on the tissue.
In theory this method would have the same color palette, stability, and general appearance as the natural patterns of the species. But the designs would not be particularly limited.
Obviously this assumes the reptiles have natural patterning and that they have been able to find the chemicals that allow changing patterns. This would probably require them to have periods when their skin is thin enough for accidental splashing of herbal tea or similar to a visible effect later. Which would make applying patterns easier and less painful.
You can always use freeze branding.
As seen on http://www.wildlife.state.nm.us/fishing/fisheries-management/ it totally works on scales:
It's simple, all it really requires is ability to get something really, really cold. Pretty doable with technology from XVIII century. If they are hot-climate, then even ice might work on them that way.